Atrial fibrillation is one of the most common cardiac arrhythmia. Health consequences associated with atrial fibrillation include decreased cardiac output, less regular ventricular rhythm, the formation of blood clots in the atrial appendages, and an increased incidence of stroke. While some drugs are available for the treatment of atrial fibrillation, they have a number of side effects which reduce their therapeutic utility.
Unlike patients afflicted with ventricular fibrillation, patients afflicted with atrial fibrillation are conscious. The pain associated with the administration of the defibrillation shock can be severe, and there is a need for means of carrying out atrial defibrillation in a manner that is less painful to the patient being treated.
Numerous patients are afflicted with both atrial and ventricular arrrhythmias. For such patients, it would be desirable to provide a single device that can carry out both atrial and ventricular defibrillation with minimum shock strength, and with minimal surgical intervention.
U.S. Pat. No. 5,549,641 to Ayers et al., issued Aug. 27, 1996, describes an atrial cardioverter and method in which atrial arrhythmia is first detected. If no arrhythmia is detected, then no action is taken. If arrhythmia is detected, the system proceeds through determining whether the arrhythmia is an atrial flutter, or a more severe arrhythmia, and a therapeutic pulse ranging from pace pulses or low energy cardioversion through intermediate and high energy cardioversion is given. A disadvantage of this system is that it is not capable of preventing an arrhythmia prior to occurrence thereof. Other systems which provide different levels of therapeutic pulses, but only after the onset of an arrhythmia, are described in U.S. Pat. No. 4,375,817 to Engle et al., U.S. Pat. No. 4,869,252 to Gilli, and U.S. Pat. No. 5,350,401 to Levine.
A problem with the aforesaid devices is that therapy begins only after the onset of arrhythmia. It would be preferable to have a device that incorporated prognostic features and preventive therapy to prevent arrhythmia from initiating, and, if arrhythmia should initiate, to promptly treat the arrhythmia.